Replace v-html with the gl-icon component in time_ago.vue

What does this MR do?

This MR replaces v-html with the GlIcon component in app/assets/javascripts/pipelines/components/pipelines_list/time_ago.vue.

Relates to #241862 (closed).

Screenshots

The affected component is the duration/time_ago component shown on the pipeline list.

1. Go to a project with pipelines
2. Go to the pipeline overview
3. Check that the timer and calendar icons are rendered properly (and changed to the GitLab icon style)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team